problem with boost and tranny

i bought a 96 GSX (automatic=/) with an aftermarket intercooler, exaust, and headers the other day it had some problems with building boost, and had REALLY bad turbo lag and only getting 13psi floored. me and a friend replace the exaust to turbo gasket and that solved that problem. now we are building around 20 pounds of boost. and we cannot find any sort of boost controller, id like to be running about 10-15psi.

but now the new problem is that the car is seeming too only want to shift at 3000rpm. so i have to let my foot off the gas around 2500 for it to shift right.

before the new gasket it was having prouble shifting from first to second around 4500 rpm+. seemed like it was missing the gear. soo once again had to let my foot off the gas for it to shift.

if anyone has any input that would be awesome

k i figured it out. there was something wrong with my waste gate and it was closed all the time. so it was building up too much pressure and the fuel wasnt getting enough air after 3000rpms so it would stall.

so i had to plug the bleed off hose from the waste gate, and relpace 2 tubes that were basically collapsed and now its working awesome. 8psi and shifts great.